Growth, body composition, lipid profile, and peroxidation, physiological stress, and blood metabolic indicators in Labeo rohita fed a fish oil replacement with blended linseed and sunflower oils

Effect of sunflower oil (SFO) + linseed oil (LnO) (1:1) blend as a replacement for fish oil (FO) in the diet of Labeo rohita (initial weight 20.37 +/- 0.16 g) was evaluated for a 90-day feeding trial. Five isonitrogenous (30% crude protein) and isolipidic (11% crude lipid) experimental diets with different levels of SFO + LnO (0, 25, 50, 75, and 100%) were formulated. Growth performance, survival, and feed utilization were not significantly affected by the dietary treatments. Similarly, FO replacement did significantly influence hepatosomatic index (HSI), viscerosomatic index (VSI), and the whole body proximate composition. However, significant changes were observed in fatty acid composition (P < 0.05). In the muscle and liver, saturated fatty acids (SFA) and n-3 polyunsaturated fatty acids (PUFA) decreased, while monounsaturated fatty acids (MUFA) and n-6 PUFAs increased with the increasing rate of replacement. Despite the reduction in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as a result of the replacement of dietary FO, these fatty acids were still detected in considerable amounts even after total replacement. Hematology parameters, serum biochemistry, serum lipid profile, and plasma stress biomarkers were not significantly influenced by the dietary treatments. Antioxidant enzyme activities did not significantly change; however, lipid peroxidation level was significantly reduced by the FO replacement with SFO + LnO blend. In conclusion, substituting fish oil with SFO + LnO blend demonstrated promising results, maintaining growth, feed efficiency, and overall health status in L. rohita. Replacement of dietary FO with SFO + LnO resulted in a significant reduction in LC-PUFAs such as EPA and DHA in fish; however, these fatty acids were still detected in a considerable amount even at total replacement, which confirmed the capacity of L. rohita to bioconvert dietary LNA to EPA and DHA in fish.